The duty
An electric wire-rope hoist lifts 5,000 kg at 8 m/min through a gearbox and rope drum with an overall efficiency of 80 %. The hoist works FEM 2m class: 40 % cyclic duration factor and up to 240 starts per hour. The brake must hold a 125 % test load and stop the load quickly when lowering.
Step 1 · Motor power
The next EMPD S4 brake motor is EBM-D160M-4-11: 11 kW, 1,465 rpm, MN 71.7 Nm, starting torque 2.5 × MN. The load torque reflected to the motor shaft is 53.3 Nm when hoisting (74 % of rated torque), leaving a comfortable reserve for the S4 duty.
Step 2 · Brake torque
For hoists we select the brake at about 200 % of motor torque. The catalogue selection for this rating is EBD-19 at 144 Nm. The static load torque at the motor is 42.6 Nm, so even with the 125 % test load the brake holds with a safety factor of 144 ÷ (1.25 × 42.6) = 2.7.
Step 3 · Energy per stop: the check most selections skip
When lowering, the load drives the motor and the brake must absorb the kinetic energy of everything rotating plus the work done by the descending load during the stop.
The EBD-19 thermal table allows about 4.8 kJ per stop at 240 stops/h (interpolated between 12 kJ at 100 stops/h and 3.8 kJ at 300 stops/h). The design uses about 40 % of that, a margin of 2.4×, so the friction lining stays within its rating at full duty. The load stops within about 8 mm of travel plus the brake response time.
Step 4 · Details that make it work
- Switch the DC brake on the DC side. Switching on the AC side lengthens the engagement time roughly six-fold, which lets the load creep and multiplies the energy per stop.
- Thermistors in the winding protect against overheating at 240 starts an hour, where a current relay alone reacts too slowly.
- Manual release lever lets maintenance lower the load safely after a power loss.
- If the hoist moves to an inverter drive, feed the brake from a separate supply, never from the inverter output.
Result
An 11 kW S4 brake motor with a 144 Nm DC brake meets the duty with margin on power, holding torque and brake heat. The same three checks apply to every hoist enquiry EMPD receives, and our engineers confirm them before quoting.
Application study: an engineering example worked by EMPD with catalogue data. Your application is confirmed by our engineers before quotation. Send us your duty.
